Research Field


Research Subjects


Research projects


Selected publications












Research Field:    Electronic and optical properties of semiconductor materials and nanostructures for optoelectronic and photovoltaic applications.


Research Subjects:


·       Surface photovoltage (SPV) and photoconductivity spectroscopy studies of

i) III-V nanostructures (quantum wells, superlattices, quantum wires, quantum dots) for optoelectronic applications (emitters, detectors);

ii) materials for photovoltaics  - a) dilute nitrides - InGaAs(Sb)N, GaAsSbN grown by  Liquide phase epitaxy and  Molecular beam epitaxy; b) a-Si/c-Si; c) Si Nanowires; d) InAs/GaAs QDs for intermediate band solar cells

·       Calculations of the reflectivity and transmission spectra of multi-layer structures with rough interfaces.


Research projects:


Current projects:


·        National Research Program E+: Low Carbon Energy for the Transport and Households (grant agreement D01-214/2018). Component 1: Storage and conversion of renewable energy , 
WP 1.4 Other methods for conversion and storage of renewable energy. Task 1.4.1: New materials, technologies and systems for solar energy conversion; Subtask Innovative solar cells based on new dilute nitride materials


Past projects

·        COST action 1406 MultiscaleSolar - Multiscale in modelling and validation for solar photovoltaics.(2015-2019)
Multiscalesolar creates a new network of experts defragmenting knowledge on nanostructures applied to photovoltaics by combining existing research activities to address key issues in in next generation solar cells raised by academic and industrial end users.


·        Advanced Materials for next generation solar cells (2016-2018)
Contract No. ДКОСТ 01/16 with the National Science Fund 
Перспективни материали за следваща генерация слънчеви елементи)

Leader: assoc. Prof. Dr. Vesselin Donchev


·        Advanced materials based on A3B5 dilute nitrides for next generation solar cells
Sofia University research fund, contract No. 71/2015
Перспективни материали на основата на разредени нитриди на А3В5 съединения за следваща генерация слънчеви елементиФНИ на СУСв.Кл.Охридски”, договор 71/2015г.)

Leader: assoc. Prof. Dr. Vesselin Donchev


·        Investigation of A3B5 dilute nitrides for next generation solar cells
Sofia University research fund, contract No. 114 /2016
(Изследване на разредени нитриди на А3В5 съединения за следваща генерация слънчеви елементи, ФНИ на СУ “Св.Кл.Охридски”, договор /2016г.)
Leader: assoc. Prof. Dr. Vesselin Donchev


 Selected publications:


1.             Milanova, V. Donchev, K. J. Cheetham,  Zh. Cao, I. Sandall, G. M. Piana, O. S. Hutter, K. Durose, A. Mumtaz
Single-junction solar cells based on p-i-n GaAsSbN heterostructures grown by liquid phase epitaxy
Solar energy 208, 659-664 (2020) 

2.             M. Milanova, V. Donchev, B. Arnaudov, D. Alonso-Álvarez, P. Terziyska
GaAsSbN-based p-i-n heterostructures for solar cell applications grown by liquid-phase epitaxy
J. Mat. Sci.:Materials in Electronics 31 (3), 2073–2080  (2020)

3.             V. Donchev
Surface photovoltage spectroscopy of semiconductor materials for optoelectronic applications
Mater. Res. Express 6 103001 (2019)

4.             V. Donchev, S. Georgiev, A. Aho, M. Guina
Surface photovoltage study of GaInAsN layers for photovoltaic applications
J. Phys.: Conf. Series 1186
(1), 012003 (2019)
(oral presentation at the 20th Jubilee International School on Condensed Matter Physics, 03-07.09.2018 Varna, Bulgaria

5.             M. Milanova V. Donchev, P. Terziyska, E. Valcheva, S. Georgiev, K. Kirilov, I. Asenova, N. Shtinkov, Y. Karmakov, I. G. Ivanov
Investigation of LPE grown dilute nitride InGaAs(Sb)N layers for photovoltaic applications
AIP Conference Proceedings 2075, 140004 (2019);
(oral presentation at the 10th Jubilee International Conference of the Balkan Physical Union 29-30.08.2018, Sofia, Bulgaria)

6.             M. Milanova, V. Donchev, K. L. Kostov, D. Alonso-Álvarez, P. Terziyska, G. Avdeev, E. Valcheva, K. Kirilov and S. Georgiev
Study of GaAsSb:N bulk layers grown by liquid phase epitaxy for solar cells applications
Mat. Res.Express 6 (7) 075521 (2019)

7.             V. Donchev, S. Georgiev, I. Leontis and A. G. Nassiopoulou
Effective Removal of Surface Recombination Centers in Silicon Nanowires Fabricated by Metal-Assisted Chemical Etching
ACS Appl. Energy Mater. 1 (8) 3693–3701 (2018)

8.             V. Donchev , M. Milanova, I. Asenova, N. Shtinkov, D. Alonso-Álvarez, A. Mellor, Y. Karmakov,  S. Georgiev and  N. Ekins-Daukes
Effect of Sb in thick InGaAsSbN layers grown by liquid phase epitaxy
J. Cryst. Growth 483  140–146  (2018)

9.             M. MilanovaV. Donchev, K. Kostov, D. Alonso-Бlvarez, E.Valcheva, K. Kirilov, I. Asenova, I. G. Ivanov, S. Georgiev and N. Ekins-Daukes
Experimental study of the effect of local atomic ordering on the energy band gap of melt grown InGaAsN alloys 
SemicondSciTechnol  32 (8) 085005 (2017)

10.        V. Donchev, I. Asenova, M. Milanova, D. Alonso-Álvarez, K. Kirilov, N. Shtinkov, I. G. Ivanov, S. Georgiev, E. Valcheva and  N. Ekins-Daukes
Optical properties of thick GaInAs(Sb)N layers grown by liquid-phase epitaxy
J. Phys.: Conf. Ser. 794, 012013 (2017)

11.        V. Donchev, M. Milanova, J. Lemieux, N. Shtinkov and I. G. Ivanov
"Surface photovoltage and photoluminescence study of thick Ga(In)AsN layers grown by liquid-phase epitaxy
J.Physics:Conf. Ser. 700, 012028 (2016)

12.        V.Donchev, Ts. Ivanov, Ts. Ivanova, S. Mathews, J. O. Kim2 and S. Krishna
"Surface photovoltage spectroscopy study of InAs quantum dot in quantum well multilayer structures for infrared photodetectors”
Superlattices and Microstructures 88, 711–722 (2015)

13.        Ts. Ivanov, V. Donchev, K. Germanova, Ts. Tellaleva, K. Borissov, V. Hongpinyo, P. Vines, J. P. R. David, and B. S. Ooi
"Investigation of the optical properties of InAs/InGaAs/GaAs quantum dot in quantum well multilayer structures for infrared photodetectors”
J.Physics:Conf. Ser. 356, 012032 (2012)

14.        T. Angelova, N. Shtinkov, Ts. Ivanov, V. Donchev, A. Cantarero, Ch. Deneke, O. G. Schmidt, and A. Cros
“Optical and acoustic phonon modes in strained InGaAs/GaAs rolled up tubes"
Appl. Phys. Lett. 100 201904 (2012).

15.        V. Donchev, D. Nesheva, D. Todorova, K. Germanova, E. Valcheva
“Characterization of Si–SiOx nanocomposite layers by comparative analysis of computer simulated and experimental infra-red transmission spectra“
Thin Solid Films 520 (6) 2085–2091 (2012)

16.        Ts. Ivanov, V. Donchev, K. Germanova, P. F. Gomes, F. Iikawa, M. J. S. P. Brasil and M. A. Cotta
“Optical properties of multi-layer type II InP/GaAs quantum dots studied by surface photovoltage spectroscopy“
J. Appl. Phys. 110 , 064302 (2011)

17.        F. Iikawa, V. Donchev, Ts. Ivanov, G. O. Dias, L. H. G. Tizei, R. Lang, E. Heredia, P. F. Gomes, M. J. S. P. Brasil, M. A. Cotta, D. Ugarte, J. P. Martinez Pastor, M. M. de Lima Jr., and A. Cantarero
“Spatial carrier distribution in InP/GaAs type II quantum dots and quantum posts
Nanotechnology 22, 065703 (2011).

18.        V Donchev, Ts Ivanov, T Angelova, A Cros, A Cantarero, N Shtinkov, K Borisov, D Fuster, Y Gonzalez and L Gonzalez
”Surface photovoltage and photoluminescence spectroscopy of self-assembled InAs/InP quantum wires
J. Phys. : Conf. Ser. 210 012041 (2010)

19.        Ts Ivanov, V Donchev, T Angelova, A Cros, A Cantarero, N Shtinkov, K Borissov, D Fuster, Y Gonzalez and L Gonzalez
Characterisation of multi-layer InAs/InP quantum wires by surface photovoltage and photoluminescence spectroscopies”
J. Phys. : Conf. Ser. 253, 012043 (2010)

20.        V. Donchev, Ts. Ivanov, K. Germanova, K. Kirilov
“Surface photovoltage spectroscopy – an advanced method for characterization of semiconductor nanostructures” (Review)
Trends in Applied spectroscopy 8, 27- 66 (2010)

21.        Ts. Ivanov, V. Donchev, K. Germanova and K. Kirilov
“A vector model for analyzing the surface photovoltage amplitude and phase spectra applied to complicated nanostructures”
J.Phys.D: App.Phys. 42 (13) 135302 (2009)

22.        V. Donchev, K. Kirilov, Ts. Ivanov, K. Germanova
“A surface photovoltage spectroscopy study of GaAs/AlAs complicated nanostructures with graded interfaces”
J. Appl. Phys. 101 (10) 124305 (2007)

23.        Ts. Ivanov, V. Donchev, Y. Wang, H. S. Djie, and B. S. Ooi
“Interdiffused InAs/InGaAlAs quantum dashes-in-well structures studied by surface photovoltage spectroscopy”
J. Appl. Phys. 101 (11) 114309 (2007)

24.        V. Donchev, K. Kirilov, Ts. Ivanov, K. Germanova
”Surface photovoltage phase spectroscopy– a handy tool for characterisation of bulk semiconductors and nanostructures”
Mat. Sci. & Engineering B: Solid State Materials for Advanced Technology 129 (1-3) 186-192 (2006)

25.        V. Donchev, K. Germanova, N. Shtinkov, S. J. Vlaev
”Electronic structure and optical properties of AlAs/GaAs superlattices containing embedded GaAs quantum wells with abrupt and graded interfaces”
in: Frontal Semiconductor Research , ed. Oliver T. Chang (Nova Science Publishers, Inc. New York, 2006) Chap. 2, pp.25-60.

26.        K. Kirilov, V. Donchev, Tsv. Ivanov, K. Germanova, P. Vitanov and P. Ivanov
”A surface photovoltage spectroscopy system used for minority carrier diffusion length measurements on floating zone silicon”
J. Optoel. & Adv. Mat. 7 (1) 533-536 (2005).

27.        Ts Ivanov, V. Donchev, K Bachev, Y-H Ding, Y Wang, H S Djie and B S Ooi
“Bandgap engineering of InAs/InGaAlAs quantum dashes-in-well laser structures: A surface photovoltage spectroscopy study”
J. Phys. : Conf. Ser. 113, 012033 (2008)