Electrical and Optical Properties of (n)ZnO/(p)CdTe Heterojunction and Its Performance as a Photovoltaic Converter

Abstract

Thin film heterojuctions of the type (n)ZnO/(p)CdTe with different doping concentration were prepared by vacuum evaporation, and their electrical and optical properties, both in dark and under illumination at room temperature as well as elevated temperatures, were studied. Different junction parameters such as ideality factors, barrier heights, Richardson constant, short-circuit current, etc. were determined from I -V characteristics. These parameters were found to change significantly on hydrogenation and annealing of the junctions and also on variation of temperature. The structures showed the change of the photovoltaic (PV) effect, giving a fill factor of 0.57 for hydrogen (H)-treated with an open-circuit voltage of 345 mV and a short-circuit current density of 75.72 × 10 −4 mA·cm −2 and 0.42 for untreated with an open-circuit voltage of 244 mV and a short-circuit current density of 52.00 × 10 −4 mA·cm −2 for doping concentrations of N a = 2.43 × 10 16 /cm 3 (2.53% Sb doped CdTe) and N d = 3.88 × 10 15 /cm 3 (2.74% Al doped ZnO). The junctions were found to possess a series resistance as high as 437 for an untreated sample and 95 for H-treated samples even under illumination. Proper doping, annealing, and hydrogenation are necessary to reduce the series resistance so as to achieve an ideal solar cell.

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.…”

Characterization of mono-crystalline silicon solar cell

“…For an p-n junc tion solar cell, the relation between V oc and I sc can be defined as follows [24,25]: (7) with (8) where E go is the band gap at T = 0 K, I is the total output current and I o is the diode saturation current. In our V oc nkT q Fig.…”

Study of Au, Ni-(n)ZnSe Thin Film Schottky Barrier Junctions

“…The open-circuit voltage and short-circuit current are strongly dependent on the series resistance as well as on the diode ideality factor as per the well-known equations [25],…”