The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). The standard establishes the principles that an entity shall apply to report useful information to users of financial statements about the nature, amount, timing, and uncertainty of revenue and cash flows from a contract with a customer.

The rights and benefits to the Company’s OLED technology are conveyed to the customer through technology license agreements and material supply agreements. The Company believes that the licenses and materials sold under these combined agreements are not distinct from each other for financial reporting purposes and as such, are accounted for as a single performance obligation. Accordingly, total contract consideration, including material, license and royalty fees, is estimated and recognized over the contract term based on material units sold at the estimated per unit fee over the life of the contract.

Various estimates are relied upon to recognize revenue. The Company estimates total material units to be purchased by its customers over the contract term based on historical trends, industry estimates and its forecast process. Additionally, management estimates the total sales-based royalties based on the estimated net sales revenue of its customers over the contract term. Management is using the expected value method to estimate the material per unit fee.

For the three months ended June 30, 2019 and 2018, the Company recorded 98% and 93% of its revenue from sales of materials and 2% and 7% from the providing of services through Adesis, respectively. For the six months ended June 30, 2019 and 2018, the Company recorded 97% and 94% of its revenue from sales of materials and 3% and 6% from the providing of services through Adesis, respectively.

The following table provides information about assets and liabilities associated with our contracts from customers (in thousands):

	As of June 30, 2019
Accounts receivable	$	66,952
Short-term unbilled receivables		730
Long-term unbilled receivables		575
Short-term deferred revenue		82,472
Long-term deferred revenue		44,651

Short-term and long-term unbilled receivables are classified as other current assets and other assets, respectively, on the Consolidated Balance Sheet. The deferred revenue balance at June 30, 2019 will be recognized as materials are shipped to customers over the remaining contract periods. The significant customer contracts (individually representing greater than 10% of revenue) expire in 2022. As of June 30, 2019, the Company had $9.0 million of backlog associated with committed purchase orders from its customers for phosphorescent emitter material. These orders are anticipated to be fulfilled within the next 90 days.

Significant changes in the unbilled receivables and deferred liabilities balances during the period are as follows (in thousands):

	Six Months Ended June 30, 2019
	Unbilled Receivables Increase (Decrease)			Deferred Revenue (Increase) Decrease
Balance at December 31, 2018	$	1,020		$	(122,567	)
Revenue recognized that was previously included in deferred revenue		—			63,337
Increases due to cash received		—			(68,213	)
Cumulative catch-up adjustment arising from changes in estimates of transaction price		—			320
Unbilled receivables recognized		1,064			—
Transferred to receivables from unbilled receivables		(779	)		—
Net change		285			(4,556	)
Balance at June 30, 2019	$	1,305		$	(127,123	)