High-Efficiency P-I-N Microcrystalline and Micromorph Thin Film Silicon Solar Cells Deposited on LPCVD Zno Coated Glass Substrates

Abstract

The authors report on the fabrication of microcrystalline silicon p-i-n solar cells with efficiencies close to 10%, using glass coated with zinc oxide (ZnO) deposited by low pressure chemical vapor deposition (LPCVD).LPCVD front contacts were optimized for p-i-n microcrystalline silicon solar cells by decreasing the free carrier absorption of the layers and increasing the surface roughness. These modifications resulted in an increased current density of the solar cell but also in significantly reduced fillfactor (FF) and open-circuit voltage (Voc). In order to avoid these reductions, a new surface treatment of the ZnO is introduced. It transforms profoundly the surface morphology by turning the typical V-shaped valleys of the LPCVD ZnO into U-shaped valleys and by erasing from the surface small-sized pyramids and asperities. As a result, for fixed deposition parameters, the p-i-n microcrystalline silicon solar cell efficiency increased from 3.3% to 9.2%Further optimization of the microcrystalline silicon solar cell on this 'new' type of LPCVD ZnO front contact has led to an efficiency of 9.9%.

Microcrystalline silicon solar cells: effect of substrate temperature on cracks and their role in post‐oxidation

“…Although ''cracks'' have been reported in the past by several authors [11][12][13][14], their full role in limiting the device performance has only been evidenced recently [15][16][17][18]. In our laboratory, mc-Si:H p-i-n solar cells are deposited on glass covered by low pressure chemical vapor deposition zinc oxide (LPCVD ZnO), which possesses a natural texture, with as-grown pyramids at the surface, exhibiting typically a V-shape structure [19,20].…”

“…An existing approach to decrease crack density is to modify the surface morphology from V-shape to U-shape by applying a surface treatment [14,21]. However, the surface treatment decreases the light scattering capabilities of the LPCVD ZnO [22] because of the change in morphology.…”

Nanoimprint Lithography for High-Efficiency Thin-Film Silicon Solar Cells

“…To optimize the morphology for the growth of the cells, the ZnO surface was treated for 20 min with an argon plasma. 32 A negative UV-NIL stamp was fabricated by nanoimprinting of the master ZnO texture into a UV sensitive sol-gel lacquer (Ormocer from Micro Resist Technology GmbH). After curing under UV light and demolding, this stamp was coated with an antisticking layer and used to transfer the positive structure onto a UV-NIL lacquer on a borosilicate glass substrate.…”

Control of CVD-deposited ZnO films properties through water/DEZ ratio: Decoupling of electrode morphology and electrical characteristics

“…In order to fill this gap, we base our understanding on previous work showing that the morphology observed at the surface of LP-MOCVD ZnO results from a combination of both nucleation-and kinetic-driven phenomena [8][9][10][11][12][13][14][15][16][17]. In fact, it was demonstrated that temperature induced inter-facet diffusion could lead to the selection of different crystallographic PO [8].…”

“…As-grown LP-MOCVD ZnO presents V-shaped valleys separating the pyramidal features, which causes defective mc-Si growth, leading to decreased open-circuit voltage (V oc ) and fill factor (FF), and hence to lower cell efficiency [10]. One possible approach to circumvent these issues is to use a surface plasma treatment to transform the V-shaped valleys into smoother U-shaped valleys that are well-adapted for good-quality absorber material deposition [11]. However, such plasma treatment leads to a decrease in the scattering ability of the film.…”