Hole-Selective TMO Contact Structure With Low Optical Absorption
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Solution Overview
Problem
Existing solar cell technologies face limitations in energy conversion efficiency due to light-absorbing selective contact layers, particularly in crystalline silicon cells and tandem devices, where transition metal oxide layers are unstable and introduce absorption issues.
Innovation Solution
A multilayer structure comprising a n-type high-work function transition metal oxide layer and a thin n-type low-work function transition metal oxide layer forms a hole-selective contact structure with a perovskite absorber layer, enhancing stability and reducing optical absorption, suitable for both single-junction and monolithic tandem solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If highly doped Si based films are used as selective contact, then hole selectivity is improved, but light absorption increases reducing energy conversion efficiency
Solution Approach 1:
The patent changes the material parameters from highly doped Si to TMO layers with specific work functions (n-type high-work function TMO for hole selectivity, n-type low-work function TMO for low absorption). This parameter change allows achieving hole selectivity through work function mismatch rather than heavy doping, thereby reducing light absorption and improving energy conversion efficiency.
2Reliability
If n-type high work function TMO is used as hole-selective contact, then hole transport is improved, but stability in air deteriorates
Solution Approach 1:
The patent creates a composite structure with two TMO layers: n-type high-work function TMO (for hole transport) combined with n-type low-work function TMO (for stability). The low-work function TMO layer acts as a protective interface that prevents degradation of the high-work function TMO when exposed to air, while maintaining the hole transport functionality through the high-work function layer.
3Reliability
If contact layers with significant light absorption coefficient are used in tandem junctions, then electrical contact is improved, but optical transmission deteriorates
Solution Approach 1:
The patent changes the material parameters of contact layers in tandem junctions from conventional light-absorbing materials to TMO layers with optimized work functions and low absorption coefficients. The n-type high-work function TMO provides electrical contact functionality while the n-type low-work function TMO ensures optical transparency, allowing both electrical and optical requirements to be satisfied simultaneously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a stable and efficient solar cell configuration with reduced light absorption, enabling higher energy conversion efficiencies and avoiding the use of volatile materials like indium tin oxide, while maintaining low-temperature processing and conformal film deposition.
Implementation Method 1
the n-type high-work function transition metal oxide layer (TMO) is able to form a hole transport layer (HTL) from the perovskite absorber layer
Implementation Method 2
the thin n-type low-work function transition metal oxide layer is able to prevent the instability of the HTL by offering an efficient capping effect
Implementation Method 3
This capping layer thus guarantees the tunneling phenomena that ensures that the high-work function TMO layer can efficiently collect the holes of the first absorber cell
Implementation Method 4
the n-type high-work function TMO layer is thus part of the recombination junction replacing the conventional p-doped Si layer in the tunnel junction
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A multilayer structure (100) for photovoltaic applications, the multilayer structure (100) comprising: - a n-type high-work function transition metal oxide (TMO) layer (3) deposited on a support structure (6), - a thin n-type low-work function transition metal oxide (TMO) layer (2) covering the n-type high-work function TMO layer (3), and - a first absorber cell (1) based on a perovskite material on the n-type low-work function TMO layer (2), the n-type high-work function TMO layer (3) and the thin n-type low-work function TMO layer (2) forming a hole-selective contact structure (200).