Detailed Balance Limit of Efficiency of p-n Junction Solar Cells

Abstract

In order to find an upper theoretical limit for the efficiency of p-n junction solar energy converters, a limiting efficiency, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of hole-electron pairs is radiative as required by the principle of detailed balance. The efficiency is also calculated for the case in which radiative recombination is only a fixed fraction fc of the total recombination, the rest being nonradiative. Efficiencies at the matched loads have been calculated with band gap and fc as parameters, the sun and cell being assumed to be blackbodies with temperatures of 6000°K and 300°K, respectively. The maximum efficiency is found to be 30% for an energy gap of 1.1 ev and fc = 1. Actual junctions do not obey the predicted current-voltage relationship, and reasons for the difference and its relevance to efficiency are discussed.

Intermediate band position modulated by Zn addition in Ti doped CuGaS2

“…This band allows the existence of two energy gaps, which originate absorption of two photons in addition to the photon absorbed in the host semiconductor band-gap; increasing, in this way, the absorption and making the photovoltaic material more efficient than before. The limiting efficiency of intermediate band solar cell is as high as t] = 0.632 [1], greater than the calculated maximum theoretical efficiency of r\ = 0.406 [2] for a conventional solar cell with a single band-gap.…”

Optical Properties of ZnO/ZnS and ZnO/ZnTe Heterostructures for Photovoltaic Applications

“…Unfortunately, the ZnO band gap (3.4 eV) is too large for use in efficient photovoltaic devices. 13 Nonetheless, this has not prevented numerous attempts to construct photovoltaics from this material, with schemes such as n-ZnO/p-CdTe thin film heterojunctions, 14,15 ZnO/CdSe composites, 16 n-ZnO/p-Cu 2 O heterojunctions, 17,18 n-ZnO/p-Si heterostructures, 19,20 ZnO-nanocrystal/organic-polymer hybrid photovoltaics, [21][22][23][24][25][26][27][28] and ZnO-nanocolumns as electrodes for dye-sensitized photoelectrochemical cells. 29 One idea to reduce the band gap of ZnO is to stack it with another environmentally benign and abundant material, such as ZnS.…”

Functional Materials for Sustainable Energy Technologies: Four Case Studies

“…These two loss processes limit the conversion efficiency of a PV cell to around 44 %. Shockley and Queisser showed [16] that if other important loss processes are also taken into account, such as the grain boundary recombination of photoexcited electron-hole pairs, resistive losses, reflection from the surface, and some other factors, the maximum theoretical efficiency a solar cell made from a single material can achieve in full unconcentrated sunlight is only 32 %.…”

“…[16] A critical feature of rapidly developing Genera- [18] ) tion III PV systems (Figure 6) is that their module efficiencies can potentially exceed the Shockley-Queisser limit by employing a multijunction design or exploiting novel physical phenomena to separate the photogenerated charge carriers. [23] Several approaches exist to increase the efficiency of PV devices to above 32 %, including multijunction solar cells, multiple energy level solar cells and multiple exciton generation solar cells.…”