Macroscopic Nonuniformities in Metal Grids Formed by Cracked Film Lithography Result in 19.3% Efficient Solar Cells

Abstract

Cracked film lithography (CFL) is an emerging method for patterning transparent conductive metal grids. CFL can be vacuum-and Ag-free, and it forms more durable grids than nanowire approaches. In spite of CFL's promising transmittance/ grid sheet resistance/wire spacing tradeoffs, previous solar cell demonstrations have had relatively low performance. This work introduces macroscopic nonuniformities in the grids to improve the short-circuit current density/fill factor tradeoff in small area Cu(In,Ga)Se 2 cells. The performance of optimized baseline grids is matched by CFL grids with microscopic openings and macroscopic patterns, culminating in a 19.3% efficient cell. Simulations show that uniform CFL grids are enhanced by patterning because it leads to better balance among shadowing, grid resistance, and transparent conductive oxide resistance losses. Thin-film module efficiency calculations are performed to highlight the performance gains that metal grids can enable by eliminating the transparent conductive oxide losses and widening monoliths. Adding the patterned CFL grids demonstrated in this work to CIGS modules is predicted to reach 0.7% higher efficiency (absolute) than screen-printed grids.

Patterning Metal Grids for GaAs Solar Cells with Cracked Film Lithography: Quantifying the Cost/Performance Tradeoff

“…To estimate grid sheet resistance and better understand device operation, we performed finite element method simulations . We assumed that a uniformly generated current source ( J SC ) was conducted laterally through the absorber and window (Figure S1), which had a combined sheet resistance of 50 Ω sq –1 (as measured by transfer length measurements).…”

Comment on “Introduction of a Novel Figure of Merit for the Assessment of Transparent Conductive Electrodes in Photovoltaics: Exact and Approximate Form”

“…Equation (13) allows current density losses to be referred to experimental results for TCEs of arbitrary thickness using Fresnel calculations. [ 11 ] Moreover, experimental T TCE (λ) and T TCE,ref (λ) data from glass/TCE structures can be used, provided the corresponding experimental J MP,ref is known. Similar to FOM TCE , φ Anand can also be adapted to experimental cells using two band gaps: A spectral band gap for the T TCE,avg integral and a J SC / V OC ‐matching band gap for the J SC,DB and J 0,DB integrals.…”

“…Equation (15) assumes that monoliths reduce current density but not voltage. The impacts of monolith contact resistance and shunt conductance can additionally be computed [ 11 ] using the previously reported functions for FF. [ 13 ] Figure 5 shows that for T TCE,avg = 0.9 and R sh,TCE = 10 Ω sq −1 , FOM TCE,mono has an optimal L of 0.4 cm, which is close to the L used in real thin‐film modules.…”

“…For instance, a reference solar cell with maximum power current density J MP,ref and a TCE with transmittance T TCE,ref (λ) can be used to predict the current density that same reference cell would have if it were fabricated with a new TCE of transmittance T TCE (λ) Equation ( 13) allows current density losses to be referred to experimental results for TCEs of arbitrary thickness using Fresnel calculations. [11] Moreover, experimental T TCE (λ) and T TCE,ref (λ) data from glass/TCE structures can be used, provided the corresponding experimental J MP,ref is known. Similar to FOM TCE , ϕ Anand can also be adapted to experimental cells using two band gaps: A spectral band gap for the T TCE,avg integral and a J SC /V OC -matching band gap for the J SC,DB and J 0,DB integrals.…”

Flexible transparent electrodes based on metallic micro–nano architectures for perovskite solar cells

“…Besides these four key factors, appropriate work function, cost-effective material, highthroughput fabrication processing, and chemical stability should also be considered for developing high-performance flexible TEs. Among the abovementioned novel conductive materials, MMNAs have been widely equipped in silicon solar cells, 83,84 III-V photovoltaics, 85,86 Cu(In,Ga)(Se,S) 2 cells, [87][88][89] and organic solar cells, 44,[90][91][92] due to the high conductivity and tunable optical transmittance of MMNAs. However, drawbacks including high roughness, immigration of metallic ions, and degradation at the interface are faced when flexible TEs based on MMNAs are integrated with PSCs.…”