Thin silicon solar cells with SiОх /SiNx Bragg mirror rear surface reflector

Abstract

Bragg reflectors consisting of sequence of dielectric layers with a quarter wavelengths optical thickness are promising to create solar cells of third generation. SiО х /SiN x Bragg mirror (BM) at the backside of textured multicrystalline silicon solar cells was fabricated by PECVD method. BM with 9 bi-layers was optimized for the maximum reflectivity within the wavelength range Δλ = 820...1110 nm. The maximum measured reflectivity is approximately 82 %. Measured reflectivity values were compared with the simulated ones by using the transfer matrix. Effect of parameters for pyramids of several types on the total reflectivity of BM deposited on textured silicon surface was simulated. Enhancement of light absorption and external quantum efficiency in the longwave part of the spectrum (λ > 940 nm) was observed, and it was explained as increase of the photon absorption length. The influence of BM on passivation of SC rear surface was explored. The cell back contact was formed by Al diffusion through BM to the μc-Si wafer and promoted by a pulsed laser. For SC with BM, the efficiency 13.75 % is obtained comparatively with efficiency 13.58 % for SC without BM.

Thin-film ‘Thermal Well’ Emitters and Absorbers for High-Efficiency Thermophotovoltaics

“…For example, a distributed Bragg reflector, which is commonly used as a high quality mirror, supports a photonic band gap, which can be positioned at photon energies just below the electronic band gap of the PV cell 61 62 . In fact, the concept of incorporating a Bragg reflector in a PV module is not new and has been used in the past as a way to recycle photons in various PV cells 63 64 65 66 67 68 . Although it is impossible to completely eliminate metal, since electrical contacts are needed to extract charge carriers, a recent study has shown that it is ideal to minimize the contact area between the PV cell and the metal contacts to reduce recombination losses 69 .…”

Wpływ Tylnego Lustra Dielektrycznego Na Działanie Krzemowych, Cienkowarstwowych Ogniw Słonecznych Otrzymanych Metodą Epitaksji Z Fazy Gazowej

“…Można to osiągnąć przez teksturyzację powierzchni przedniej/tylnej ogniwa i/lub wytworzenie lustra na tylnej powierzchni odbijającego niskoenergetyczne fotony [5]. Taka modyfikacja pozwala na absorpcję fotonów, które w przeciwnym razie przeszłyby przez ogniwo bez interakcji [6].…”