Solar cells open circuit voltage

The optical properties of electrodeposited, polycrystalline CdTe have been found to be similar to those of single-crystal CdTe [257]. In 1982, Fulop et al. [258] reported the development of metal junction solar cells of high efficiency using thin film (4 p,m) n-type CdTe as absorber, electrodeposited from a typical acidic aqueous solution on metallic substrate (Cu, steel, Ni) and annealed in air at 300 °C. The cells were constructed using a Schottky barrier rectifying junction at the front surface (vacuum-deposited Au, Ni) and a (electrodeposited) Cd ohmic contact at the back. Passivation of the top surface (treatment with KOH and hydrazine) was seen to improve the photovoltaic properties of the rectifying junction. The best fabricated cell comprised an efficiency of 8.6% (AMI), open-circuit voltage of 0.723 V, short-circuit current of 18.7 mA cm, and a fill factor of 0.64. 

Fig. 3.17. Structure of the 9.35%-efflcient Basol solar cell, with open-circuit voltage 0.73 V, short-circuit current 20 mA cm, and fiU factor 0.64. (Reproduced from [86])...

Illumination of solar cells causes a reduction of efficiency and fill factor, as a result of light-induced creation of defects (Staebler-Wronski effect. Section 1.1.2.5). This reduction is halted after several hundred hours of illumination. The reduction is correlated with solar cell thickness. A large intrinsic layer thickness leads to a large reduction of efficiency and fill factor compared to a small intrinsic layer thickness. The solar cell properties can be completely recovered by annealing at about 150°C. The open circuit voltage and short circuit current decrease only slightly. 

The PV characteristics of the CIGS2 thin-film solar cell on opaque Mo back contact, as measured at the NREL under AM 1.5 conditions, were as follows short-circuit current density sc of 20.88 mA/cm2, open-circuit voltage 1% of 830.5 mV, fill factor FF of 69.13%, and PV conversion efficiency // of 11.99%. 

Kymakis E, Amaratunga GAJ (2003). Photovoltaic cells based on dye-sensitisation of single-wall carbon nanotubes in a polymer matrix. Solar Ener. Mater. Solar Cells 80 465 172.Kymakis E, Alexandrou I, Amaratunga GAJ (2003). High open-circuit voltage photovoltaic devices from carbon-nanotube-polymer composites. J. Appl. Phys. 93 1764-1768. 

He, I. Zhong, C. Huang, X. Wong, W.-Y. Wu, H. Chen, L. Su, S. Cao, Y., Simultaneous enhancement of open-circuit voltage, short-circuit current density, and fill factor in polymer solar cells. Adv. Mater. 2011, 23, 4636-4643. 

Rand BP, Burk DP, Forrest SR (2007) Offset energies at organic semiconductor heterojunctions and their infiuence on the open-circuit voltage of thin-film solar cells. Phys Rev B 75 115327... 

Cheyns D, Rand BP, Heremans P (2010) Organic tandem solar cells with complementary absorbing layers and a high open-circuit voltage. Appl Phys Lett 97 3... 

Potscavage WJ, Sharma A, Kippelen B (2009) Critical interfaces in organic solar cells and their influence on the open-circuit voltage. Acc Chem Res 42 1758... 

Guha S, Yang J, Nath P, Hack M (1986) Enhancement of open circuit voltage in high-efficiency amorphous-silicon alloy solar-cells. Appl Phys Lett 49 218 Hack M, Shur M (1985) Physics of amorphous-silicon alloy p-i-n solar-cells. J Appl Phys 58 997... 

Brabec CJ, Cravino A, Meissner D, Sariciftci NS, Eromheiz T, Rispens MT, Sanchez L, Hummelen JC (2001) Origin of the open circuit voltage of plastic solar cells. Adv Eunct Mater 11 374... 

Lenes M, Wetzelaer G, Kooistra FB, Veenstra SC, Hummelen JC, Blom PWM (2008) Fullerene bisadducts for enhanced open-circuit voltages and efficiencies in polymer solar cells. Adv Mater 20 2116... 

Vandewal K, Tvingstedt K, Gadisa A, Inganas O, Manca JV (2010) Relating the open-circuit voltage to interface molecular properties of donor acceptor bulk heterojunction solar cells. Phys Rev B 81 125204... 

There have been many investigations of photoinduced effects in -Si H films linked to material parameters. Changes have been observed in the carrier diffusion length, unpaired spin density, density of states in the gap, and infrared transmission. The transition from state A to B seems to be induced by any process that creates free carriers, including x-ray radiation and injection (double) from the electrodes. Because degradation in a solar cell is accentuated at the open-circuit voltage conditions, the A to B transition occurs upon recombination of excess free carriers in which the eneigy involved is less than the band gap. It has been pointed out that this transition is a relatively inefficient one and the increase in spin density takes place at a rate of 10-8 spins per absorbed photon. 

Photoelectrochemical cells with polythiophene film as an active electrode and a lead plate as a counter electrode in Pb (C104) acetonitrile electrolyte has an open circuit voltage of 0.8 V, short circuit current of 2 x 10 4 A cm-2, efficiency coefficient of 0.03%, fill factor of 15% [194]. The absorption and photosensitivity spectra of such a cell are shown in Fig. 24. The small bathochromic shift in the longwave region for photosensitivity may be related to the photogeneration of the charge carriers via surface states. The photosensitivity maximum is close to the maximum solar intensity. The parameters exceed the ones obtained with polyacetylene. 

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