To improve the efficiency of solar panels, it is necessary to increase the open-circuit voltage Uoc, the short-circuit current ISC, and the fill factor FF. These three factors are often mutually restrained. If one of them is increased unilaterally, it may reduce the other, so that the overall efficiency is not improved but decreased. Therefore, it must be taken into consideration when selecting materials and designing processes, and strive to maximize the product of the three factors.

    The open circuit voltage UOC increases with the increase of the energy bandwidth Eg, but on the other hand, the short circuit current density decreases with the increase of the energy bandwidth Eg. As a result, a peak of solar cell efficiency can be expected to occur at a certain Eg. The highest efficiency is expected to be achieved by using materials with Eg values ​​between 1.2 and 1.6 eV to make solar cells. Direct bandgap semiconductors are preferable for thin-film batteries because they absorb photons near the surface.

    The diffusion length of photons increases slightly with the increase of temperature, so the photogenerated current also increases with the increase of temperature, but the UOC decreases sharply with the increase of temperature. The fill factor decreases, so the conversion efficiency decreases with increasing temperature. With the increase of irradiance, the short-circuit current increases linearly, and the maximum power increases continuously. Focusing sunlight on a solar cell allows a small solar cell to generate a large amount of electricity. Another factor that has a significant impact on UOC is the semiconductor doping concentration. The higher the doping concentration, the higher the UOC. However, when the impurity concentration in silicon is higher than 1018/cm3, it is called high doping. The band gap shrinkage caused by high doping, the impurity cannot be fully ionized and the lifetime of minority carriers is reduced, etc., are collectively called high doping effect, and should also be treated avoid.