| dc.description.abstract | Abstract
This study used Electron cyclotron resonance chemical vapor deposition (ECR-CVD) to discuss epi-Si thin films deposited on silicon substrates of homojunction solar cell applications. ECR-CVD is the high density plasma sources for thin film deposition process equipment. The principle is that electrons under the influence of magnetic fields will do coning motion, when angular frequency and incidence of microwave frequency match each other, it will absorb microwave energy to make gas atom ionization for high density plasma. Compared with PECVD, it has many advantages such as higher deposition rate, lower working pressure, lower ion bombardment effect, and no pollution of electric shock…etc.
This study will deposit high quality epi-Si thin film on c-Si substrate by ECR-CVD. Traditionally, monocrystalline silicon solar cells form doping layers with high temperature diffusion process and ion implant. This experiment will prepare emitter layers and the back surface field (BSF) by chemical vapor deposition in very low temperature(< 200 ℃). We deposited 20nm p-type epi-Si layers on the c-Si substrate through modulation of gas mixing ratio, process temperature, microwave power, thin film thickness as well as front and after process improvement. Under this single-layer plane structure without anti-reflective layer, the conversion efficiency is 8.679%. Otherwise, transferring the back surface thin-film micro-structure from microcrystalline to amorphous, we improved open circuit voltage and short-circuit current because of hydrogenated amorphous silicon with better surface passivation reducing minority carrier recombination from long-wavelength photon on back surface. The result with anti-reflection in plane structure have conversion efficiency (η) =13.67%; open circuit voltage (Voc) =556.3mV; short circuit currents (Jsc) =37.18mA ; fill factor (FF) =66.07%. In the pyramid structure, we have conversion efficiency (η) =17.69% open circuit voltage (Voc) =563.5mV; short circuit currents (Jsc) =42.36mA; fill factor (FF) =74.12%.
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