A.D. Maslov – Junior Research Scientist, 

Department «Micro- and nanoelectronics», Ryazan State Radio Engineering University named after V.F. Utkin E-mail: Maslov.a.d@mail.ru

N.V. Vishnyakov – Ph.D.(Eng.), Associate Professor, 

Department «Micro- and nanoelectronics», Ryazan State Radio Engineering University named after V.F. Utkin

E-mail: rcpm-rgrtu@yandex.ru; rcpm@rsreu.ru

In this work we present a method to find recombination rates in the active layers and at the interface of heterojunction amorphous/crystalline HIT solar cells. The method is based on experimental measuring dependences of open-circuit voltage on light intensity and temperature and solving discontinuity equation at open-circuit conditions. The method is a consequent extension of Grover's method proposed for CIGS solar cells. The developed method, compared to Grover's approach considers recombination in the amorphous layer.

We present an algorithm to calculate recombination rates that clearly demonstrates the necessary pre-experiment parameters.

For experimental investigating HIT structure we developed a measuring complex that includes methods of current-voltage characteristics (I-V), capacitance-voltage characteristics (C-V), their temperature and photoelectrical dependences. To control recombination centers we chosen DLTS method. For determination of spatial localization of recombination centers it is necessary to implement experimental measurements using this complex and some calculations to find: width of the depletion region, contact potential at the aSi:H/c-Si interface, doping and excess charge carrier concentration, dependence of open-circuit voltage on temperature and intensity, dependence of open-circuit voltage on average generation rate. The obtained data allow to calculate recombination rates in the depletion region, amorphous layer, quasi-neutral base and at the a-Si:H/c-Si interface. DLTS investigation showed presence of 3 deep energy levels (DL) with activation energies E1 = 0.07±0.02 eV, E2 = 0.36±0.02 eV, E3 = 0.72±0.03 eV and concentrations Nt·d (E1) = 1.7·1010 cm−2, Nt·d (E2) = 1.7·1010 cm−2 и Nt·d (E3) = 1.7·1010 cm−2 respectively (Nt is the DL’s concentration and d is the width where an emission of charge carriers from deep energy level takes place). Investigation of photoelectical and thermoelectrical characteristics and consequent calculations of recombination rates showed that dominating values correspond to recombination in the depletion region Rd = 8.875·1018 cm−2 s−1 and heterointerface a-Si:H/c-Si Ri = 1.381·1018 cm−2 s−1. According to the data we suggested that recombination centers are localized in the depletion region near the interface.

Therefore the proposed method allows to define localization of dominating recombination centers in the active layers of HIT structure, that reduce efficiency of the solar cell. This actions provides technological and design recommendations for manufacturing.

1. Global renewable energy consumption over the long-run. https://ourworldindata.org/renewable-energy [08.09.2019].
2. Spisok solnechnykh elektrostantsii Rossii. https://ru.wikipedia.org/wiki/Spisok_solnechnykh_elektrostantsii_Rossii [08.09.2019]. (in Russian)
3. Tekhnologiya proizvodstva geterostrukturnykh solnechnykh elementov. http://www.hevelsolar.com/process-proizvodstva/ [08.09.2019]. (in Russian)
4. Farenbrukh A., Byub R. Solnechnye elementy: Teoriya i eksperiment: Per. s angl.. Pod red. M.M. Koltuna. M.: Energoatomizdat. 1987. 280 s. (in Russian)
5. Pavlov L.P. Metody izmereniya parametrov poluprovodnikovykh materialov: Uchebnik dlya vuzov. Izd. 2-e, pererab. i dop. M.: Vysshaya shkola. 1987. 239 s. (in Russian)
6. Arafat, Yeasir°&°Mohammedy, Farseem°&°Hassan, Shahidul. Optical and Other Measurement Techniques of Carrier Lifetime in Semiconductors. International Journal of Optoelectronic Engineering. 2012. 2. 5-11. DOI:10.5923/j.ijoe.20120202.02.
7. Poindexter, Jeremy°&°Barnard, Edward°&°Kurchin, Rachel°&°Buonassisi, Tonio. Charge-carrier lifetime measurements in early-stage photovoltaic materials: intuition, uncertainties, and opportunities. 2018. arXiv:1805.05832 [cond-mat.mtrl-sci].
8. Sachit°Grover, Jian V.°Li, David L.°Young, Paul°Stradins, Howard M.°Branz. Reformulation of solar cell physics to facilitate experimental separation of recombination pathways. Appl. Phys. Lett. 2013. 103, 093502. DOI:10.1063/1.4819728.
9. Sara°Olibet, Evelyne°Vallat-Sauvain, Christophe°Ballif. Model for a-Si:H/c-Si interface recombination based on the amphoteric nature of silicon dangling bonds. PHYSICAL REVIEW B. 2007. 76, 035326. DOI: 10.1103/PhysRevB.76.035326.
10. Maslov A.D., Litvinov V.G., Ermachikhin A.V. The measuring systems of semiconductor structures and its software. Proceeding of the 2015 International Siberian conference on control and communications (SIBCON). Omsk (Russia): Omsk State Technical University. 21−23 May 2015. DOI: 10.1109/SIBCON.2015.7147318.
11. Vishnyakov N.V., Vorobev Yu.V., Gudzev V.V., Ermachikhin A.V., Kusakin D.S., Litvinov V.G., Maslov A.D., Mishustin V.G., Tolkach N.M., Kholomina T.A.Razvitie metodov issledovaniya poluprovodnikovykh materialov i pribornykh struktur mikro- i nanoelektroniki. Vestnik Ryazanskogo gosudarstvennogo radiotekhnicheskogo universiteta. 2017. № 2 (60). S. 164−170. (in Russian)
12. Maslov A.D., Vishnyakov N.V., Vikhrov S.P., Gudzev V.V., Ermachikhin A.V., Shilina D.V., Litvinov V.G., Mishustin V.G., Terukov E.I., Titov A.S. Study of deep levels in a HIT solar cell. Semiconductors. V. 52. № 7. P. 926−930. DOI: 10.1134/S1063782618070254.
13. Kusakin D.S., Litvinov V.G., Rybin N.B., Litvinova V.S., Shchelushkin V.N., Khudysh A.I. Lokalnoe issledovanie C-V- kharakteristik solnechnogo elementa na osnove p-Si s modifitsirovannoi poverkhnostyu. Vestnik Ryazanskogo gosudarstvennogo radiotekhnicheskogo universiteta. 2017. № 3 (61). S. 137−142. DOI: 10.21667/1995-4565-2017-61-3-137-142. (in Russian)
14. Vikhrov S.P., Vishnyakov N.V., Maslov A.D., Mishustin V.G., Romanov A.G. Izmerenie raspredeleniya vstroennykh elektricheskikh polei v poluprovodnikovykh barernykh strukturakh. Vestnik Ryazanskogo gosudarstvennogo radiotekhnicheskogo universiteta. 2018. № 4 (66). S. 23−29. DOI: 10.21667/1995-4565-2018-66-4-2-23-29. (in Russian)