Physics of ultrathin photovoltaics

Abstract

The authors consider physical properties of ultrathin photovoltaics with thickness (≲1μm) smaller than both the depletion width and diffusion length, applicable to the cases of amorphous, polycrystalline, and nanostructured devices. Three phenomena underlie the unique physics of such systems: (1) lateral screening by conducting electrodes, (2) leakiness due to defect assisted tunneling, and (3) gigantic capacitive energy conducive to shunting breakdown. The authors give numerical estimates and discuss practical implications of these phenomena.

Modelling of degradation/recovery phenomena in CdS/CdTe ultrathin film solar cells

“…In this case, the SCR is reduced by the forward biasing and the BC region can slightly increase. This is in agreement with all the conceptual studies in literature and the physical theory considered above [1,14]. The reverse bias diminishes the W b by extending the SCR, whereas the forward bias reduces the strength of F and creates a back barrier at the BC.…”

“…The thickness of such devices (d) is comparable with the width of SCR (W) and carrier diffusion length (L n ). Karpov et al [1] have studied the unique physics of ultrathin photovoltaics (PV) by assuming W [ d. They considered that an ultrathin device resembles a capacitance with a dielectric inside it. In another approach, Kosyachenko and Toyama [2] have analysed the thin-film devices with d = 2.7 lm and showed that the influence of BC on the carrier transport in SCR can be ignored if the concentration of uncompensated acceptors, N ad = 5 9 10 15 cm -3 , and the depletion widths of SCR (W = 0.6-0.8 lm) do not overlap with the depletion width of the BC (W b = 0.2 lm).…”

3D Single Gaas Co-Axial Nanowire Solar Cell for Nanopillar-Array Photovoltaic Device

“…Reverse bias measurements from p-i-n and p-n diodes also show markedly different behaviour: the p-i-n diode breaks down at much larger reverse-bias voltage (approximately 27 V) than the p-n diode (approximately 21 V) for all temperatures studied. In addition, the reverse-bias breakdown voltage of the p-n diode increases with decreasing temperature, which is consistent with a Zener (tunneling) breakdown mechanism, whereas the breakdown voltage of the p-i-n structures exhibits little temperature dependence, suggesting contributions from tunneling and avalanche mechanisms [11] Overall, these results indicate that tunneling or leakage currents are more significant in the p-n diode [12], and that the diode quality factor and breakdown behavior are readily controlled during nanowire growth by the introduction of the i-layer as in planar structures [13,14].…”

“…The transport properties are calculated using the drift diffusion model. using such a semi-classical approach for the nanowire size considered in this work has been discussed in [11], [12]. In the calculation, we enabled the Shockley-Read-Hall recombination and concentration dependent mobility.…”

“…Furthermore, we have shown that interconnected GaAs nanowire photovoltaic elements to form nano-pillar array photovoltaic can serve as more efficient power sources. These coaxial GaAs nanowire photovoltaic elements provide a new nanoscale test bed for studies of photo induced energy/charge transport and artificial photosynthesis [10], and might find general usage as elements for powering ultra low power electronics [11] and diverse nanosystems [12,13] or nanopillar array photovoltaic system.…”