Solar Cell Hole Transport Layer Ionic Compound
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Solution Overview
Problem
Solar cells with a hole transport layer containing Spiro-OMeTAD and Li-TFSI suffer from poor high-temperature durability, while using Li-TFSI alone is insufficient for achieving high photoelectric conversion efficiency.
Innovation Solution
Incorporating an ionic compound with a Spiro-OMeTAD cation and a TFSI anion in the hole transport layer, maintaining a metal concentration of 1000 ppm or lower, and using a different organic semiconductor to enhance both photoelectric conversion efficiency and high-temperature durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a hole transport layer containing Spiro-OMeTAD and Li-TFSI is used, then photoelectric conversion efficiency is improved, but high-temperature durability deteriorates due to metal precipitation
Solution Approach 1:
The patent changes the chemical composition parameters of the hole transport layer by replacing Li-TFSI with an ionic compound containing TFSI anion and organic semiconductor cation. This parameter change maintains the necessary ionic conductivity and doping effects for high photoelectric conversion efficiency while eliminating lithium metal precipitation that causes poor high-temperature durability.
Solution Approach 2:
The patent uses a composite ionic compound formed by the combination of TFSI anion and organic semiconductor cation (such as Spiro-OMeTAD cation). This composite material provides both the ionic conductivity needed for high efficiency and the thermal stability required for good high-temperature durability, resolving the contradiction between the two performance aspects.
2Reliability
If Li-TFSI is not used, then high-temperature durability is improved, but photoelectric conversion efficiency becomes insufficient
Solution Approach 1:
The patent introduces an ionic compound as an intermediary substance that provides the necessary ionic conductivity and doping function without using Li-TFSI. The ionic compound acts as a mediator that delivers the beneficial effects of lithium salts for efficiency while avoiding the harmful precipitation effects, thus enabling both high efficiency and good high-temperature durability.
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 solar cell achieves higher photoelectric conversion efficiency and improved high-temperature durability by using an ionic compound with a Spiro-OMeTAD cation and a TFSI anion, maintaining low metal concentration, and employing a different organic semiconductor.
Implementation Method 1
Solar cells generate photocarriers (electron-hole pairs) by photoexcitation
Implementation Method 2
the carrier density cannot be sufficiently increased due to the precipitated metal as a dopant
Data Source
Figure 1
AI summary
The present invention aims to provide a solar cell having high photoelectric conversion efficiency and excellent high-temperature durability, and an organic semiconductor material. The present invention relates to a solar cell having: an electrode; a counter electrode; a photoelectric conversion layer disposed between the electrode and the counter electrode; and a hole transport layer disposed between the photoelectric conversion layer and the counter electrode, the hole transport layer containing an ionic compound that contains an organic semiconductor cation and a fluorine-containing compound anion, the hole transport layer having a metal concentration of 1,000 ppm or lower.