n ITO spray / p InP Solar Cells

Solar cells have been prepared by ITO spray deposition on InP single crystal. Solar power conversion efficiency reaches 10% under AMl conditions on 20 mm2 areas. Typical values for Voc and Icc are respectively 500 mV and 28 mA/cm2.The pyrolysis temperature optimum is 360°C. The weight composition of the starting spray solution is Sn/In = 10%. Two p-type substrates have been studied: po(300K) = 2.1018 cm−3 and 1016 cm−3. The best results have been obtained using the less doped InP but the back contacts on this material are not perfectly controlled. The ITO-InP interface has been investigated by EBIC profile measurements. The junction is not localized at the metallurgical interface but is around 0.8 μdeeper into InP. This recalls the result of the same investigation on ITO sputtering/InP cells and allows to propose the same model of buried homojunction for both types of cells. I-V measurements versus temperature show that, two transport processus are competitive: generation-recombination and tunnel effects. For the best cells, the first process is dominant. This agrees with the proposed model of buried homojunction. Spectral response measurements show a low energy abrupt cut off at the InP gap value. The flat aspect of the spectral response is typical of an heterojunction or of an homojunction with a very low surface recombination velocity.