The Device Level BZO Preparation And Application On The Solar Cell Research

Zinc oxide (ZnO) is a very promising semiconductor material,and it has a wide directband gap of3.37eV at room temperature.Compared with the ITO,ZnO has comparableelectrical conductibity and optical transmittance.Due to high electrical conductivity andoptical transmittance,abundant raw materials,non-toxic,ZnO thin films as transparentconductive oxide (TCO) have been widely concerned in solar cells.In Si thin-film solarcells,As textured light traping front electrodes and back reflectors in Si thin-film solar cells,ZnO films can greatly improve the efficiency and stability of cells and speed up theindustrialization process.In this paper, the Boron-doped Zinc Oxide (BZO) films wereprepared on glass using diborane(B2H6) as the doping gas by metal organic chemical vapordeposion.It has gained a good performance when the films were applied in a-Si:H solarcells. Detailed study of ZnO:B films was listed below.The BZO films with high transmittance (>75%) and low resistivity (1.0×10-3Ω cm)can be obtained on a23cm×23cm glass substrate using diborane(B2H6) as the doping gas bymetal organic chemical vapor deposition. The effect of deposition parameters (such assubstrate temperature,reaction pressure,doping concentration of diborane, proportion of thereactants and thickness of films) on the microstructure,optical and electrical properties ofBZO films was investigated.The results show that the parameters of substratetemperature,reaction pressure and doping concentration of diborane greatly influence thefilm performance,especially the substrate temperature.With the inceasing of substratetemperature,the surface morphology of the BZO films gradually changes from sphere-liketo pyramid-like,and finally turns into ridge-like.The cause of this phenomenon is mainly thedifferent surface energy of BZO crystals.Doping can greatly improve the conductivity andelectrical stability.The optical band gap of BZO films gradually broadening with theincreasing of doping concentration.The BZO films growth stably and has more dense grainsat low reaction pressure,so that the adhesion between films and substrate is larger.After the90nm BZO films were applied as the back reflection electrode in a-Si:H anda-Si:Ge thin-film solar cells,the short-circuit current density of cells were improved by2.82mA/cm2and1.5mA/cm2separately and the conversion efficiency of cells wereimproved by1.3%and0.75%separately.The1000nm BZO films not only have a good textured structure,but also have low resistivity (1.6×10-3Ω cm) by using gradient growthtechnology of parametures (such as reaction pressure and doping concentration ofdiborane).Compared with SnO2films,it presents equal performance when the BZO filmswere applied as front electrodes.It laid a solid foundation for the application ofMOCVD-ZnO in Si thin-film solar cells industry.