Towards 12% stabilised efficiency in single junction polymorphous silicon solar cells: experimental developments and model predictions

Abstract

We have combined recent experimental developments in our laboratory with modelling to devise ways of maximising the stabilised efficiency of hydrogenated amorphous silicon (a-Si:H) PIN solar cells. The cells were fabricated using the conventional plasma enhanced chemical vapour deposition (PECVD) technique at various temperatures, pressures and gas flow ratios. A detailed electrical-optical simulator was used to examine the effect of using wide band gap P-and N-doped μc-SiOx:H layers, as well as a MgF2 anti-reflection coating (ARC) on cell performance. We find that with the best quality a-Si:H so far produced in our laboratory and optimised deposition parameters for the corresponding solar cell, we could not attain a 10% stabilised efficiency due to the high stabilised defect density of a-Si:H, although this landmark has been achieved in some laboratories. On the other hand, a close cousin of a-Si:H, hydrogenated polymorphous silicon (pm-Si:H), a nano-structured silicon thin film produced by PECVD under conditions close to powder formation, has been developed in our laboratory. This material has been shown to have a lower initial and stabilised defect density as well as higher hole mobility than a-Si:H. Modelling indicates that it is possible to attain stabilised efficiencies of 12% when pm-Si:H is incorporated in a solar cell, deposited in a NIP configuration to reduce the P/I interface defects and combined with P-and N-doped μc-SiOx:H layers and a MgF2 ARC.

Practical Jsc Limits for SHJ Devices: Insights From Modelling

“…We note that the extinction coefficient used in the models in this work were significantly lower than the values published in the literature [19][20][21][22], suggesting that significant improvements have been made to the optical properties of the thin film layers used in the record solar cells. In the absence of published refractive index data for layers present in these record solar cell devices, the adjusted refractive index data used in the models (see Appendix A and B) represent a reasonable estimate for optical modelling purposes (as indicated by the good match between modelled and published EQE and reflectance data).…”

“…Information regarding layer thicknesses as described in Ref. [11] and reference complex refractive indices found in the literature [19][20][21][22] and measured in-house are used as starting inputs. A thickness variation of up to ±4 nm from the published thickness data in Ref.…”

“…The original data for extinction coefficients for a-Si:H(i), nc-SiOx:H(n) and TCO are taken from Refs. [21], [20] and [19], respectively. In order to achieve a good fit to the reported EQE and reflectance data of record solar cell devices from SunDrive [9,11] and LONGi [1], the extinction coefficient (k) was multiplied by a scaling factor.…”

Sensitivity of a HIT c-Si Solar Cell to Structural Distortions of the Hydrogenated Amorphous Silicon Constituting the Front Face of the Device

“…The different results were obtained using the ASDMP software (Amorphous Semiconductor Device Modeling Program) developed by Professor Parsathi Chatterjee [7][8][9] and validated experimentally by Professor Roca's group at École polytechnique de Paris, France. The ASDMP software examines the performance of p-i-n and HIT solar cells with data from solar cell performance [10,11] by solving simultaneously Poisson's equation and the continuity equations for free electrons and free holes using finite differences and Newton-Raphson method.…”

Unravelling a simple method for the low temperature synthesis of silicon nanocrystals and monolithic nanocrystalline thin films

“…Over the past decade, we have performed detailed studies on the growth, optoelectronic properties and the application of hydrogenated polymorphous silicon (pm-Si:H) thin films to solar cells161718. Indeed, the optoelectronic properties of pm-Si:H are outstanding and allow us to envision single junction PIN solar cells with stable efficiencies of 12%19. However, the growth process of this nanostructured material is still a matter of discussion, as it can be confused with hydrogenated protocrystalline silicon (pc-Si:H), grown under conditions that for higher thicknesses result in microcrystalline material2021.…”